Continuing from the previous point, to
use mmap effectively, Elasticsearch also requires the ability to
create many memory-mapped areas. The maximum map count check checks that
the kernel allows a process to have at least 262,144 memory-mapped areas
and is enforced on Linux only. To pass the maximum map count check, you
must configure vm.max_map_count via sysctl to be at least 262144.

Alternatively, the maximum map count check is only needed if you are using
mmapfs or hybridfs as the store type for your
indices. If you do not allow the use of mmap then this
bootstrap check will not be enforced.